The Application Of AlCuFe Quasicrystallines In Al Based Metal Composite

The Al-Si alloy is widely used in various kinds of industries because of its low density,high specific strength,good heat-conducting property and excellent formability.However,with the development of the times,the properties of Al-Si alloy can't meet the need of aerospace field and motor industries.Meanwhile,the thick primary Si existed in the Al matrix will seriously decrease the comprehensive performance and mechanical properties of this alloy.But we can solve this problem effectively by adding the reinforcing particles to the Al-Si alloy which can refine grains obviously.AlCuFe icosahedral quasicrystal phase?I-phase?has high hardness,high abrasive resistance and good wettability with Al matrix,so it is particularly appropriate to be used as the strengthening phase of the Al-Si alloy.In this paper,Al₆₄Cu₂₄Fe₁₂ quasicrystalline material was prepared by conventional casting method.The effects of different cooling rates on the microstructure and phase transformation of the alloy were studied.The results show that as-cast Al64Cu24Fe12 quasicrystalline material is composed of quasicrystalline I,?-?Al-Cu?13Fe4,?-?Al?Fe,Cu??and?-?Al Cu?phases.The finer grains can be obtained in the as-cast structure because of the faster cooling rate.Meanwhile,the growth of ? phases can be restrained in samples under the faster cooling rate.However,after heat treatment at 820 ? for 6 h,almost single I phase can be obtained in all the samples.Comparing with the general cooling rate samples,the more smooth surface and pure single I phase can be discovered in the fastest cooling rate sample during the whole experiment.After preparing the high-purity quasicrystal master alloy,we prepared Al based metal composite?ZL101?reinforced with Al64Cu24Fe12 quasi-crystalline particles by a traditional casting method with proper heat treatment process.The microstructure of the composites was examined using optical microscopy,scanning,X-ray and energy dispersive spectrometer.It is found that after adding the quasi-crystalline particles to the ZL01 alloy,few quasi-crystallinephase remained and a new phase—??Al65-75Si13-26Fe3-10?phase formed,which may act as a new reinforcing phase.In particular,the mechanical behavior of this composite is remarkably improved by adding proper amount of quasi-crystalline particles.The tensile strength increases from 209 Mpa for the sample with none quasi-crystalline particles to 230,265,355 Mpa with 4 wt.%,7 wt.% and 10 wt.% of quasi-crystalline particles,respectively.Additionally,with an increase in quality fraction of the reinforcement the hardness of the composites increased up to HV=146.89 for the highest amount?10 wt.%?of added particles.However,adding a big amount?over 10 wt.%?of particles to molten ZL101 alloy will lead to the aggregation and the adhesion of reinforced particles,which resulted in the decrease of the mechanical properties.Furthermore,in the present work,a kind of “quaternary quasicrystal phase”with the composition of Al65Cu20Fe10Cr5 was prepared by replacing a part of Fe with Cr on the structure of the rapid solidified and subsequently heat-treated Al-Cu-Fe-Cr alloys.The microstructure of this phase was investigated by X-ray diffractometry?XRD?,scanning and transmission electron microscopy?SEM and TEM?.The results show that both five-fold and ten-fold electron diffraction patterns were found in Al65Cu20Fe10Cr5 phase,indicating that the Al-Cu-Fe-Cr quasicrystal phase is actually the mixture of I-phase and d-phase.The addition of chromium in substitution to iron may destabilize the I-phase and promote the formation of d-phase.And the appropriate heat treatment technology was determined for Al-Cu-Fe-Cr alloys to get the high-purity quasicrystal phases.This result has been corroborated by optical microscope?OM?,X-ray diffractometry?XRD?,energy dispersive spectrometer?EDS?and differential scanning calorimetry?DSC?.Finally,almost pure I-phase and “Al65Cu20Fe10Cr5phase” were obtained both in the Al64Cu24Fe10Cr2 and Al64Cu24Fe8Cr4 alloys after heating up to 870-900 °C and then cooled by water quenching.When the high-purity AlCuFeCr quasicrystal master alloy was obtained,we added it to the ZL101 alloy by the same process with Al64Cu24Fe12 quasi-crystalline particles.However,the microstructure of the new composite is fairly the same to the?Al64Cu24Fe12?p/ZL101 composite.Although compared with the ZL101 alloy the new composite has a greatimprovement in mechanical properties — the tensile strength increased by 39.71%,the elongation increased by 56.96% and the hardness increased by 41.11%,its whole performance is still lower than?Al64Cu24Fe12?p/ZL101 composite.So the AlCuFe quasi-crystalline particles is more suitable than AlCuFeCr quasi-crystalline particles to be used as reinforcing particles of ZL101 alloy.